Every year, almost two million episodes of pneumonia are suffered by nursing home (NH) residents across the United States, resulting in more deaths than from any other infection. Further, NH residents acquire pneumonia at a rate 6-10 times higher than older adults in the community, indicating that characteristics of these individuals and/or the NH setting put them at increased pneumonia risk. Pneumonia is an inflammatory condition usually initiated by the introduction of bacteria into the lung, such as through aspiration. In aspiration, contents from the mouth, throat, or stomach that are colonized with pathogenic bacteria are inhaled into the lungs. Poor oral hygiene is therefore a critical risk factor for pneumonia because it increases the volume and infectious nature of secretions from the mouth and throat. Considering the high rate of the pneumonia in NHs and its relationship to oral hygiene, it should come as no surprise that mouth care provided in NHs is poor. Almost 90% of residents require help with tooth brushing, yet only 16% have their teeth brushed regularly. Reasons for insufficient care include time, other priorities, existing procedures, perceptions that oral health is not vital to overall health, and fear of resistant residents. Evidece is emerging that improved oral care can prevent pneumonia. However, no studies have developed and tested a program designed specifically for widespread adoption and sustainability. Our research team has developed and pilot-tested such a program, called Mouth Care Without a Battle. Its approach is modeled after Bathing Without a Battle, which has become the standard of care in NHs across the nation. Mouth Care Without a Battle significantly increased staff knowledge and attitudes related to mouth care; improved tooth brushing and flossing; and most importantly, reduced dental plaque and gingivitis that harbor the bacteria that can cause pneumonia. Further, improved care and outcomes persisted. If Mouth Care Without a Battle is effective in reducing pneumonia, it would constitute a major advance in prevention. Therefore, the objective of this evidence-based, tested, matched pairs cluster randomized trial is to determine whether and to what extent pneumonia incidence in NH residents can be reduced by training nursing assistants and supervisory nursing staff to provide a pragmatic, system-level, comprehensive mouth care program to all NH residents, including use of a dedicated oral care aide. In doing so, the study will achieve the following specific aims: (1) compare the incidence of pneumonia in seven mouth care NHs to the incidence of pneumonia in seven control NHs for two years; (2) examine the implementation and sustainability of the mouth care program; and, secondarily, (3) compare differences in hospitalization and mortality rates, and assess the likelihood that the intervention is cost-saving. We expect this project to result in a pragmatic, system-level, comprehensive mouth care program that can be widely adopted and sustained and which will result in fewer episodes of pneumonia and related cost savings.